Traditional molecular dynamics timesteps are limited to one femtosecond by the large force constants associated with bond stretching and angle bending terms in the force field. Fortunately, thesemotions are of limited interest on longer timescales and, hence,with proper treatment they can be neglected while preserving theother properties of the simulation. Such treatment has made possible computational studies of biopolymers on significantly longer time scales than the present nanosecond range. A straightforward approach to neglecting bond stretching andangle bending is to mathematically constrain the distances associated with these degrees of freedom and, thus, restrict thesystem to the slower torsional modes. Iterative methods such asSHAKE [45] are mainly useful for constraining small fractions ofthe system.For the present case in which the majority of thedegrees of freedom are removed from the system direct solutionof the associated equations is more appropriate. These methodshave been incorporated into NAMD for both normal moleculardynamics and the overdamped dynamics of Gronbech-Jensen and Doniach [46]. While these efforts have been somewhat successful and show promisein combination with interactive molecular dynamics, further workis needed. Particularly, the flexibility lost by constraining manydegrees of freedom must be replaced by adjusting the remaining force-field parameters. Also, these methods would benefit greatlyfrom the introduction of a model treating bulk water as a continuum. Success with these methods would allow the simulation of protein folding and vastly improve response times for interactive molecular dynamics.